Unhandled exception when name or initials are blank

[mattbearman]

Monogram.svg(name: ' ')

# => Infinity (FloatDomainError)

Same with name: '' and initials: '', however initials: ' ' will render an empty background.

nil values are handled in the lib, eg:

Monogram.svg(name: nil)

# => either `initials:` or `name:` must be specified (ArgumentError)

Although I'm not sure this is the best approach. I think the best would be to return an empty, completely transparent avatar image if there are no initials/name, and have a config option to raise an error instead, default transparent avatar